Quick emplacement gun carriage mechanism

ABSTRACT

In order to convert a wheeled gun carriage between fixed emplacement thereof and a mobile towing position, each wheel is mounted to one end of a support arm which is, in turn, angularly pivoted to the side of the gun-support frame in geared connection with a rotatable shaft extending transversely through the frame in position to be rotated by movement of the vehicle utilized to tow the carriage whereby back-up movement of the towing vehicle actuates the support arms to tilt the wheels outwardly of the frame to effect the lowering thereof into fixed emplacement on the ground and whereby subsequent forward movement of the towing vehicle actuates the support arms to return the wheels to the vertical position required to permit the normal towing of the carriage.

United States Patent King [4 1 May 16, 1972 [54] QUICK EMPLACEMENT GUN CARRIAGE MECHANISM Primary Examiner-Stephen C. Bentley AttorneyHarry M. Saragovitz, Edward J. Kelly, Herbert Berl [72] Inventor: Leonard L. King, Rock Island, [I]. and Albert Arnold Jr. [73] Assignee: The United States of America as represented by the Secretary of the Army [5 7] ABSTRACT In order to convert a wheeled gun carriage between fixed emplacement thereof and a mobile towing position, each wheel is mounted to one end of a support arm which is, in turn, angularly pivoted to the side of the gun-support frame in geared connection with a rotatable shaft extending transversely through the frame in position to be rotated by movement of the vehicle utilized to tow the carriage whereby back-up movement of the towing vehicle actuates the support arms to tilt the wheels outwardly of the frame to effect the lowering thereof into fixed emplacement on the ground and whereby subsequent forward movement of the towing vehicle actuates the support arms to return the wheels to the vertical position required to permit the normal towing of the carriage.

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QUICK EMPLACEMENT GUN CARRIAGE MECHANISM BACKGROUND OF THE INVENTION This invention relates to the emplacement of a mobile gun carriage and is more particularly directed to means for rapidly converting the mobile support for the carriage to a fixed ground support capable of withstanding the recoil forces imparted thereto during the firing of the gun.

In gun carriages wherein the frame utilized to support the gun is mounted between a pair of wheels and consequently must be in a fixed position relative to the ground while the gun is being fired in order to insure the desired accuracy, the necessity for elevating the frame to lift the wheels off the ground and substitute a fixed support base therefor is customarily accomplished by one or more jacks. The dependance on such accessories not only complicates the emplacement of the gun but, more importantly, also detracts from the rapidity with which it can be relocated in the event of enemy action. Furthermore, where the combined weight of the gun and support frame therefor cannot be handled by manually operated jacks, the necessary power is usually provided by relatively bulky generators which require more elaborate maintenance procedures than those which can ordinarily be followed under combat conditions.

Accordingly, it is an object of this invention to provide a simple, rugged, and reliable mobile gun carriage which can be readily converted between a mobile towing position and a fixed firing position far more rapidly than has heretofore been possible.

It is also an object of this invention to provide a relatively large caliber gun with a wheeled carriage which can be rapidly emplaced in a fixed position on the ground without the need for manual or power-operated jacks.

Another object of this invention is to provide a wheeled gun carriage, as aforesaid, wherein the required rapid conversion between mobile and fixed support positions can be readily accomplished by simultaneously tilting both wheels outwardly or inwardly relative to the sides of the frame.

An additional object of the present invention is the provision of a system for emplacing a wheeled gun carriage wherein the weight of the gun and the support frame therefor provides the energy required to tilt the wheels in the direction in which the frame will be lowered into contact with the ground.

Still another object of this invention is to provide a. gun carriage, as aforesaid, which can be equilibrated so that the lowering of the gun-support frame into contact with the ground will provide energy which can be stored to participate in the subsequent raising of the frame to the mobile support position.

A further object of the present invention lies in the provision of a mechanical system for fixedly emplacing a mobile gun carriage wherein the lowering and raising movement of the gun supporting frame can be initiated either by the transporter vehicle utilized to tow the carriage or by the personnel assigned to operate the gun.

An important object of this invention is to provide a gun emplacement system, as aforesaid, wherein the rate of change in the angular relationship of the wheels relative to the ground during the tilting movement thereof can be resiliently varied to enhance the lowering and raising of the gun-support frame.

SUMMARY OF THE INVENTION It has been found that the foregoing objects can best be attained if the tow bar to which the transporter vehicle attaches is slidably disposed in the rear end of the carriage frame in geared connection with a transversely extending rotatable shaft. Each end of the shaft is, in turn, geared to one end of a longitudinal support arm which extends along the side of the frame at at acute angle relative to the ground to terminate in a wheel at the other end thereof. In addition, support arms are respectively attached to opposite sides of the frame so as to pivot about an axis at right angles to the longitudinal axis of the rotatable shaft. Thus, rotation of the shaft in either direction will tilt both wheels about the areas of contact thereof with the ground in opposite directions relative to the sides of the frame. Each support arm also houses a torsion bar in geared connection with the pivot member to which the support arm is mounted. These torsion bars are arranged to be actuated during the lowering and raising of the frame to vary the rate of change in the angular relationship between the wheels and the ground during a portion of the tilting movement thereof. The tow bar is arranged to be releasable locked to the frame and the end extending therein is provided with a follower device for compressing one or more equilibrator springs seated within the interior of the frame.

Thus, once the tow bar is unlocked and pushed inwardly relative to the frame, the interaction of the gears therein will begin to pivot the support arms in the direction required to tilt the wheels outwardly of the sides of the frame whereupon the combined weight of the gun and the support frame will produce the energy required to continue such tilting. When the energy stored in the torsion bars exceeds the vertical component of the load on the wheels, such bars unwind to accelerate the tilting of the wheels and thereby reduce the time required to bring the support pads on the underside of the frame into contact with the ground to complete the fixed emplacement of the carriage. When the frame is to be restored to a mobile towing position, the tow bar is pulled outwardly thereof, either manually or by the transporter vehicle utilized to provide the towing, thereby actuating the gearing to pivot the support arms in the direction required to tilt the wheels inwardly relative to the sides of the frame. During the initial tilting of the wheels, the torsion bars are rewound to resiliently support the weight of the carriage. The continued movement of the transporter vehicle and the action of the equilibrator springs, which were previously compressed during the lowering of the frame, provide the energy required to continue the tilting of the wheels until the frame is fully raised to the towing position thereof.

BRIEF DESCRIPTION OF THE DRAWINGS The exact nature of the invention as well as other objects and advantages thereof will be readily apparent from consideration of the following specification relating to the an nexed drawings wherein:

FIG. 1 is a perspective view of the gun carriage with the wheels in the upright vertical position required to permit towing by a separate vehicle;

FIG. 2 is an enlarged top plan view of the major portion of the gun-support frame partially broken away to show the structural details of the equilibrator springs and the relationship between the tow bar and the rotatable shaft;

FIG. 3 is a sectional view taken along line 33 in FIG. 2 to show the geared connection between the tow bar and the rotatable shaft which extends transversely through the frame;

FIG. 4 is a sectional view taken along line 4-4 in FIG. 2 to show the interior of one of the support arms and the angle at which it is attached to the side of the frame;

FIG. 5 is a sectional view taken along line 5-5 in FIG. 4 to show the gear structure which serves to unload and load the torsion bar in the support arm during the lowering and raising of the frame, the end of the support arm being shown in full for ease in illustration;

FIG. 6 is a sectional view taken along line 6-6 in FIG. 4 to show the details of the connection between the support arm and the adjacent side of the frame;

FIG. 7 is a perspective view similar to that of FIG. I but showing the carriage with the wheels tilted to the position required to provide the fixed emplacement thereof on the ground;

FIG. 8 is a fragmentary sectional view through the enlarged end of the support arm similar to that of FIG. 5 but showing the relationship between the gear segment on the torsion bar and the C-shaped stop when the wheels have been fully tilted to provide the fixed emplacement shown in FIG. 7; and

FIG. 9 is a perspective view of the pivot member utilized to connect the support arm to the side of the frame.

DESCRIPTION OF A PREFERRED EMBODIMENT As shown in FIG. 1 of the drawings wherein similar reference characters have been employed to designate corresponding parts throughout, the gun carriage to which the present invention is applicable essentially comprises a generally triangular frame 12 of isoceles configuration with a base leg 14 of greater structural rigidity than the isoceles legs. The ability of frame 12 to support a gun (not shown) is additionally strengthened by an integral central strut 16 extending between the apex of the isoceles legs and the base leg 14. Hereinafter, references to directions are to be construed in accordance with the orientation of the gun which is mounted on frame 12 so that the muzzle or forward end thereof extends beyond the apex of the isoceles legs. Thus, base leg 14 is to be considered as located rearwardly of the apex of the isoceles legs. A generally rectangular housing 18 extends rearwardly from base leg 14 to axial alignment with strut 16 to slidably receive a tow bar 20 terminating in a ring shaped end 22 arranged to be engaged by the pintle on a transporter vehicle (not shown). In order to lock tow bar 20 against movement relative to housing 18 during the towing of the carriage, a hollow stud 24 (FIG. 3) is threadably inserted in housing 18 in position to seat a locking pin 26 and a spring 28 in abutment therewith for biasing one end of pin 26 into releasable engagement with a mating recess 30 in the periphery oftow bar 20. A pull ring 32 at the opposite end of locking pin 26 enables the latter to be manually disengaged from tow bar 20 once the towing movement of the carriage has been halted.

Extending rearwardly and outwardly from the ends of base leg 14 is a trapezoidal subframe 36 connected to opposite sides of housing 18. At each end of subframe 36 and the forward apex of frame 12 is a vertically adjustable support pad 38. In the mobile position of the carriage, frame 12 is supported between a pair of wheels 40 attached to longitudinally extending support arms 42 respectively geared to the ends of base leg 14 in a manner to be described hereinafter. Wheels 40 are preferably provided with conventional rubber tires 43 and are rotatably mounted on axles 44 (FIG. 2) extending outwardly from the respective sides of support arms 42 adjacent the forward ends thereof. The diameter of wheels 40 is such that frame 12 is supported thereby in a travel position at a height which will prevent support pads 38 from contacting the ground regardless of the unevenness of the terrain over which the gun and carriage are being towed.

A longitudinal rack gear 46 is suitably pinned to the end of tow bar 20 within housing 18, as indicated at 48 in FIGS. 2 and 3, and extends into meshing engagement with a pinion gear 50 fixedly secured to one end of a vertical shaft 52 which is, in turn, rotatably mounted within base leg 14 in the area intersected by housing 18. Shaft 52 also carries a worm gear 54 located above pinion gear 50 in meshing engagement with a worm wheel 56 fixedly mounted on an elongated rotatable shaft 58 extending through base leg 14 from one end thereof to the other.

The opposite ends of base leg 14 are rectangularly recessed, as indicated at 60 in FIG. 2, to provide space for a miter bevel gear segment 62 fastened to the end of shaft 58in meshing engagement with a corresponding miter bevel gear segment 64 pinned, as at 65, to an end ofa cylindrical sleeve 66. The latter is, in turn, mounted on a transverse pin 68 rotatably seated in the sidewalls of recess 60. Sleeve 66 is also provided with a flange 70 extending integrally outward from the exterior periphery thereof in the direction of the open end of recess 60 to serve as a bearing surface for the end face of a hub 72 protruding from the side of support arm 42 at the end thereof opposite that on which wheel 40 is mounted.

As indicated at 74, the end of support arm 42 from which hub 72 projects is dimensionally enlarged and is provided with a substantially rectangular opening 76 therein in communication with a central bore 78 therethrough. Extending centrally outward from flange 70 is a rod 80 which passes through hub 72 and rectangular opening 76 into rotatable engagement with the sidewall of the latter. I-Iub 72 is retained in bearing contact with flange 70 by bevel gear 82 pinned to rod 80 in abutment with the interior wall surface of opening 76 and in meshing engagement with a bevel gear segment 84 which is, in turn, pinned, as at 86, to one end of a torsion bar 88 extending through support arm 42. Gear 82 is formed with a hollow cylindrical body 90 which fits into hub 72 over rod 80 and is fastened to the latter by a pin 92 which can be readily inserted into place through suitable axially aligned holes 94 in the walls of hub 72, as best shown in FIG. 5. Thus, support arms 42 are respectively attached to the opposite ends of base leg 14 for pivotal movement about an axis parallel to the longitudinal axis of frame 12 and for concurrent pivotal movement in a vertical plane about an axis at right angles to the longitudinal axis of base leg 14.

The end of torsion bar 88 opposite the geared end thereofis initially pinned to support arm 42 at 96 at a time when the carriage has been lifted sufficiently to raise wheels 40 off the ground. In this position, the inclination of support arm 42 relative to the horizontal is halted by the contact between the upper side of the gear tooth portion of segment 84 and a substantially C-shaped insert 98 fastened within rectangular opening 76, as by screws 100. The spaced ends of insert 98 terminate in oppositely facing angular stop surfaces 102 and 103 which straddle the gear tooth portion of segment 84. Thus, when gear segments 84 are in contact with upper stop surfaces 103, support arms 42 are inclined at an angle to the horizontal which does not impart any load to torsion bars 88. However, when wheels 40 are lowered into contact with the ground upon the removal of the lifting force imparted to the carriage, the weight of frame 12 plus the gun thereon will pivot support arms 42 about rods 80 thereby driving gear segments 84 to impart twisting movement to torsion bars 88 until the opposing forces are balanced. At this point, the gear tooth portion of segment 84 is positioned substantially midway of stop surfaces 102 and 103 on insert 98, as best shown in FIG. 5, and support arms 42 are inclined at a lesser angle to the horizontal which, in the support of a 4,000-lb. load, has been found to be about l8.

As shown in FIGS. 2 and 3, rack gear 46 extends below and beyond shaft 58 into fixed engagement with a follower 104 to the opposite side of which are secured the stem portions 106 of a pair of horizontally spaced pistons 108. The interior of a portion of strut 16 is hollowed out, as indicated at 110, to accommodate follower 104 and piston stems 106 while the remainder of strut 16 is provided with a pair of parallel Ion gitudinal holes 112 laterally spaced to slidably receive the head portions 114 of pistons 108. Each hole 112 seats an equilibrator spring 116 between piston head 114 and a plug 118 which is releasably retained in one of a series of detent openings 120 by means of which springs 116 may be adjusted to provide the degree of bias required to raise frame 12 and the gun thereon to the towing position thereof.

In order to emplace the gun carriage, the transporter vehicle is brought to a halt and locking pin 26 is manually lifted to disengage from tow bar 20 and permit the latter to be pushed into housing 18 in response to back-up movement of the transport vehicle. This movement of tow bar 20 actuates rack gear 46 to initiate rotation of shaft 58 thereby operating miter gear segments 62 and 64 to pivot support arms 42 about pin 68 in a clockwise direction as viewed when looking forwardly from the rear of the carriage. As a result, wheels 40 begin to tilt out of the vertical support position with the portions thereof in rolling contact with the ground moving outwardly away from frame 12 while the diametrically opposite portions of wheels 40 are being moved inwardly thereby causing frame 12 to be lowered toward the ground. During this tilting movement of wheels 40, the preloaded torsion bars 88 act on support arms 42 to force wheels 40 downwardly against the ground to impart a steering action thereto outwardly of frame 12. Since the tilting of wheels 40 and the lowering of frame 12 are mutually interdependent, such steering action serves to promote the rapidity with which frame 12 and the gun thereon can be lowered during the rolling travel imparted to the carriage by the back-up movement of the transporter vehicle. Once the tilting of wheels 40 has been initiated, the weight of the gun and support frame 12 plays a dominant role in providing the energy required to continue such tilting. In view of the angle to the horizontal at which support arms 42 are attached to the ends of base leg 14 of frame 12, the outward inclination of wheels 40 during the tilting thereof is progressively increased to improve the rapidity with which frame 12 is lowered into contact with the ground. Moreover, as wheels 40 are being tilted, the contact thereof with the ground is progressively shifted from the tread portion of the tires to the crown portion thereof thereby producing a corresponding decrease in the surface area in contact with the ground. When the vertical component of the load being carried by wheels 40 falls below the force produced by the preload on torsion bars 88, support arms 42 are pivoted about rods 80 to increase the 18 angle thereof relative to the horizontal thereby accelerating the final portion of the tilting movement of wheels to minimize the scuffing and skidding of tires 43 that would otherwise occur during this period of minimum area contact with the ground. As support pads 38 come into contact with the ground to support the weight of the carriage, bevel gear segments 84 contact stop surfaces 103 on inserts 98, as shown in FIG. 8, to complete the unwinding of torsion bars 88. At this point, the crown portions of the tires on wheels 40 are still in contact with the ground. The carriage will be properly emplaced for firing as soon as support pads 38 contact the ground and take the place of wheels 40 in supporting the weight of the gun and frame 12.

In order to return the carriage to the mobile support position thereof, the transporter vehicle is operated to pull on tow bar 20. The resulting displacement of rack gear 46 actuates gears 50, 54 and 56 to rotate shaft 58 which, in turn, actuates gear segments 62 and 64 to initiate the pivoting of support arms 42 about pin 68 in a counterclockwise direction, looking forwardly from the rear of the carriage. Since wheels 40 were left in contact with the ground at the conclusion of the lowering of the carriage, the pivotal movement of support arms 42 about pin 68 immediately begins to tilt wheels 40 and raise frame 12 off the ground thereby minimizing the period during which support pads 38 will be dragged along the ground by the pull imparted to the carriage by the transporter vehicle. As support pads 38 are being lifted off the ground and the weight of frame 12 is being shifted onto wheels 40, support arms 42 are pivoted about rods 80 to return to the previous inclination thereof relative to the horizontal thereby actuating gear segments 84 to rewind torsion bars 88 to the extent required to balance the weight of the gun and frame 12. During the subsequent raising of frame 12, equilibrator springs 116, which were compressed during the lowering of frame 12, supplement the pull of the transporter vehicle on tow bar to actuate the various gears and other components involved in tilting wheels 40.

However, if for some reason the transporter vehicle is not available, the energy provided by springs 116 is sufficient to complete the raising of the gun and frame 12 once the locking relationship between worm gear 54 and wheel 56 has been broken by actuation of rack gear 46 in response to a manual pull on tow bar 20. In the event such manual actuation is to be utilized, springs 116 are preferably preloaded by positioning plugs 118 in the particular detent opening 120 which will provide the energy required to raise frame 12 to the desired height. Once wheels 40 are fully returned to the upright position required for mobile support of frame 12, tow bar 20 will reach the position in which locking pin 26 is again in alignment with recess 30 and will automatically engage therewith under the bias of spring 28. Inasmuch as the return of support arms 42 to the normal 18 inclination required to balance frame 12 and the gun thereon leaves gear segment 84 midway of stop surfaces 102 and 103, as best shown in FIG. 5, torsion bars 88 are utilized as the suspension system for frame 12 and are free to absorb any additional load which may be imparted thereto by the vertical movements encountered during the travel thereof over rough and irregular terrain. Stop surface 102 serves to limit the twisting of torsion bars 88 and prevent damage thereto from any overstress during the towing travel of the carriage.

Thus, there is here provided a mobile gun carriage which can be quickly emplaced in a fixed firing position and returned with even greater rapidity to a mobile towing position. In fact, unlike conventional gun carriages, the present invention permits the towing travel thereof to be initiated while the frame is still emplaced on the ground. This is extremely important in the event of surprise enemy action which may require immediate relocation of the gun to another firing site. This desirable rapid conversion of the carriage between an emplaced firing position and a mobile towing position is made possible by the unusual equilibrator spring arrangement which permits the weight of the gun and the support frame therefor to participate in the lowering of the frame to the ground and to provide the major portion of the energy required to raise the frame to the mobile position thereof. Furthermore, the ability to lower and raise the carriage without the need for separate accessory equipment or additional manpower is a highly desirable improvement which will minimize the logistic problems normally encountered under combat conditions. It is also noted that the torsion bar arrangement described herein provides a highly satisfactory suspension system whose operation does not interfere with the required tilting of the wheels.

Although the present invention is explained in accordance with the preferred embodiment shown and described herein, it will also become obvious to persons skilled in the art that other forms thereof as well as changes in the particular forms described, are possible within the spirit and scope of the present invention. Therefore, it is desired that the present invention shall not be limited except insofar as it is made necessary by the prior art and by the spirit of the appended claims.

I claim:

1. In a mobile gun carriage having a frame normally supported between a pair of wheels in position to permit the carriage to be towed by a separate vehicle, the combination of,

a rotatable shaft transversely seated in the frame between the opposite sides thereof,

a pair of support arms, each having a wheel mounted at one end thereof and pivotally attached at the other end thereof to the side of the frame adjacent the end of said rotatable shaft,

a tow bar slidably mounted in the frame for forward and rearward longitudinal displacement,

first gear means for converting longitudinal displacement of said tow bar to rotation of said shaft, and

second gear means for converting rotation of said shaft to pivotal movement of said support arms about an axis parallel to the longitudinal axis of the frame whereby the wheels are simultaneously tilted in opposite directions to lower or raise the frame into and out of fixed engagement with the ground in accordance with the direction in which said tow bar is displaced.

2. The mobile gun carriage of claim 1 wherein said support arms are pivotally attached to the sides of the frame at an angle to the horizontal with the ends to which the wheels are mounted being in a lower plane than the opposite ends thereof whereby the tilting of the wheels is accomplished with a progressive outward displacement thereof relative to the sides of the frame which produces a corresponding increase in the rapidity with which the latter is lowered into contact with the ground.

3. The mobile gun carriage of claim 1 including torsion bar means in each of said support arms arranged to be preloaded by the weight of the frame and the gun thereon to provide resilient suspension therefor during the towing travel thereof.

4. The mobile gun carriage of claim 1 wherein said first gear means comprises,

gear means comprises,

a bevel gear secured to said rotatable shaft at each end thereof,

a pivot member projecting outwardly from each of said support arms for rotatable engagement in the side of the frame at a location adjacent said bevel gear, and

a bevel gear segment secured to said pivot member for meshing engagement with said bevel gear.

6. A mobile gun carriage convertible to a fixed firing position comprising,

a frame having a rotatable shaft extending transversely between the opposite sides thereof,

a pair of support arms respectively pivoted at one end thereof to opposite sides of said frame adjacent the ends of said shaft,

a wheel mounted to each of said support arms at the other end thereof,

a tow bar slidably disposed in said frame for longitudinal displacement therein,

gear means for converting longitudinal displacement of said tow bar to rotation of said shaft,

a bevel gear secured to each end of said rotatable shaft, and

a bevel gear segment secured to each ofsaid pivoted ends of said support arms in respective meshing engagement with said bevel gears on said shaft for converting the rotation thereof into pivotal movement of said arms about an axis parallel to the longitudinal axis of said frame whereby said wheels are tilted outwardly relative to the sides of said frame to permit the latter to be correspondingly lowered into contact with the ground in response to the weight of said frame and the gun thereon.

7. The mobile gun carriage of claim 6 including preloaded torsion bar means in said support arms for urging the latter to pivot about an axis perpendicular to the longitudinal axis of said frame during the concurrent pivotal movement imparted to said arms by said bevel gears at the ends of said shaft whereby the tilting of said wheels is accelerated when the vertical component of the forces imparted thereto falls below the preload of said torsion bars thereby to minimize the tendency to skid under the external forces applied to the carriage during the displacement of said tow bar.

8. The mobile gun carriage of claim 7 wherein said torsion bar means comprises,

a torsion bar pinned at one end thereof in each of said support arms,

a bevel gear segment secured to the other end of said torsion bar, and

a bevel gear fixedly secured within said support arm in meshing engagement with said bevel gear segment whereby said torsion bar is normally preloaded to the extent required to balance the weight of said frame and gun thereon.

9. A mobile gun carriage convertible between a fixed firing position and a rolling travel position comprising,

a frame having a rotatable shaft extending transversely between the opposite sides thereof,

a pair of support arms each having a wheel at one end thereof, means for pivotally connecting the opposite ends of said support arms to the respective opposite sides of said frame adjacent the ends of said rotatable shaft therein,

a tow bar slidably disposed in one end of said frame for longitudinal displacement in either direction responsive to external forces thereon,

first gear means in said frame for converting longitudinal displacement of said tow bar into corresponding rotation of said transverse shaft,

second gear means between the ends of said shaft and said pivotal connecting means in said support arms for converting rotation of said shaft to pivotal movement of said support arms about an axis parallel to the longitudinal axis of said frame whereby said wheels are simultaneously tilted in opposite directions to permit the lowering and raising of said frame into and out of fixed contact with the ground, and

preloaded torsion bar means for pivoting said support arms at right angles to the pivotal movement imparted thereto by said second gear means whereby said wheels are positively steered in the direction of the tilting thereof to facilitate the raising and lowering of the frame and the gun thereon.

10. The mobile gun carriage of claim 9 including a plurality of equilibrator springs adjustably seated in said frame, and

a follower at the end of said tow bar within said frame operatively connected with said springs for compressing said springs during the lowering of said frame into contact with the ground thereby to provide sufficient energy for raising said frame to the travel position thereof in cooperation with the external forces being applied to said tow bar.

11. The combination defined in claim 9 including,

a detent releasably engageable with said tow bar to prevent displacement thereof,

means on said detent for facilitating manual disengagement thereof from said tow bar, and

spring means for biasing said detent normally into engagement with said tow bar during the longitudinal displacement imparted thereto for returning the carriage to the rolling travel position thereof.

12. The mobile gun carriage of claim 9 wherein each of said pivotal connecting means includes a pivot member,

a cylindrical portion of said pivot member being rotatably seated in the side of said frame in parallelism with the longitudinal axis thereof in position to be rotated by said second gear means,

a flange portion projecting outwardly'from said cylindrical portion and parallel thereto to serve as a bearing surface for said support arm during the pivotal movement imparted thereto by said torsion bar means, and

a rod portion extending outwardly from the center of said flange portion into rotatable engagement with said support arm to serve as an axis for the pivotal movement thereof at right angles to the direction of the pivotal movement imparted thereto by said second gear means.

13. The mobile gun carriage of claim 9 wherein said torsion bar means comprises,

a torsion bar pinned at one end thereof within said support arm adjacent said wheel,

third gear means in said support arm for rotating said torsion bar in response to the pivotal movement of said support arm about an axis at right angles to the pivotal movement imparted thereto by said second gear means, and

stop means for halting the rotation of said torsion bar in one direction to limit the unwinding thereof after said frame has been lowered into contact with the ground and in the opposite direction to limit the additional loading imparted thereto during the rolling travel of the carriage in the event of relative motion between said frame and said support arms.

14. The mobile gun carriage of claim 13 wherein said means for pivotally connecting said support arms to the sides of said frame includes an outwardly projecting rod portion extending through said support arm in rotatable engagement therewith and wherein said third gear means in each of said support arms comprises,

a bevel gear secured to said rod portion, and

a bevel gear segment secured to the free end of said torsion means for halting the rotation of said torsion bar comprising,

bar in meshing engagement with said bevel gear whereby a C-shaped insert fixedly secured within said support arm to pivotal movement of said support am about said rod porstraddle 531d bevel gear g f f, and h tion actuates said gear segment to rotate said torsion bar a p Surface on h end of 531d Insert dmps! the P accordingly. 5 of movement of said bevel gear segment. 15. The mobile gun carriage of claim 14 including stop 

1. In a mobile gun carriage having a frame normally supported between a pair of wheels in position to permit the carriage to be towed by a separate vehicle, the combination of, a rotatable shaft transversely seated in the frame between the opposite sides thereof, a pair of support arms, each having a wheel mounted at one end thereof and pivotally attached at the other end thereof to the side of the frame adjacent the end of said rotatable shaft, a tow bar slidably mounted in the frame for forward and rearward longitudinal displacement, first gear means for converting longitudinal displacement of said tow bar to rotation of said shaft, and second gear means for converting rotation of said shaft to pivotal movement of said support arms about an axis parallel to the longitudinal axis of the frame whereby the wheels are simultaneously tilted in opposite directions to lower or raise the frame into and out of fixed engagement with the ground in accordance with the direction in which said tow bar is displaced.
 2. The mobile gun carriage of claim 1 wherein said support arms are pivotally attached to the sides of the frame at an angle to the horizontal with the ends to which the wheels are mounted being in a lower plane than the opposite ends thereof whereby the tilting of the wheels is accomplished with a progressive outward displacement thereof relative to the sides of the frame which produces a corresponding increase in the rapidity with which the latter is lowered into contact with the ground.
 3. The mobile gun carriage of claim 1 including torsion bar means in each of said support arms arranged to be preloaded by the weight of the frame and the gun thereon to provide resilient suspension therefor during the towing travel thereof.
 4. The mobile gun carriage of claim 1 wherein said first gear means comprises, a rack gear secured to the end of said tow bar within the frame, a pinion gear rotatably mounted in the frame for meshing engagement with said rack gear, a worm gear mounted in the frame for synchronous rotation with said pinion gear, and a worm wheel fixed to said rotatable shaft in meshing engagement with said worm gear.
 5. The mobile gun carriage of claim 1 wherein said second gear means comprises, a bevel gear secured to said rotatable shaft at each end thereof, a pivot member projecting outwardly from each of said support arms for rotatable engagement in the side of the frame at a location adjacent said bevel gear, and a bevel gear segment secured to said pivot member for meshing engagement with said bevel gear.
 6. A mobile gun carriage convertible to a fixed firing position comprising, a frame having a rotatable shaft extending transversely between the opposite sides thereof, a pair of support arms respectively pivoted at one end thereof to opposite sides of said frame adjacent the ends of said shaft, a wheel mounted to each of said support arms at the other end thereof, a tow bar slidably disposed in said frame for longitudinal displacement therein, gear means for converting longitudinal displacement of said tow bar to rotation of said shaft, a bevel gear secured to each end of said rotatable shaft, and a bevel gear segment secured to each of said pivoted ends of said support arms in respective meshing engagement with said bevel gears on said shaFt for converting the rotation thereof into pivotal movement of said arms about an axis parallel to the longitudinal axis of said frame whereby said wheels are tilted outwardly relative to the sides of said frame to permit the latter to be correspondingly lowered into contact with the ground in response to the weight of said frame and the gun thereon.
 7. The mobile gun carriage of claim 6 including preloaded torsion bar means in said support arms for urging the latter to pivot about an axis perpendicular to the longitudinal axis of said frame during the concurrent pivotal movement imparted to said arms by said bevel gears at the ends of said shaft whereby the tilting of said wheels is accelerated when the vertical component of the forces imparted thereto falls below the preload of said torsion bars thereby to minimize the tendency to skid under the external forces applied to the carriage during the displacement of said tow bar.
 8. The mobile gun carriage of claim 7 wherein said torsion bar means comprises, a torsion bar pinned at one end thereof in each of said support arms, a bevel gear segment secured to the other end of said torsion bar, and a bevel gear fixedly secured within said support arm in meshing engagement with said bevel gear segment whereby said torsion bar is normally preloaded to the extent required to balance the weight of said frame and gun thereon.
 9. A mobile gun carriage convertible between a fixed firing position and a rolling travel position comprising, a frame having a rotatable shaft extending transversely between the opposite sides thereof, a pair of support arms each having a wheel at one end thereof, means for pivotally connecting the opposite ends of said support arms to the respective opposite sides of said frame adjacent the ends of said rotatable shaft therein, a tow bar slidably disposed in one end of said frame for longitudinal displacement in either direction responsive to external forces thereon, first gear means in said frame for converting longitudinal displacement of said tow bar into corresponding rotation of said transverse shaft, second gear means between the ends of said shaft and said pivotal connecting means in said support arms for converting rotation of said shaft to pivotal movement of said support arms about an axis parallel to the longitudinal axis of said frame whereby said wheels are simultaneously tilted in opposite directions to permit the lowering and raising of said frame into and out of fixed contact with the ground, and preloaded torsion bar means for pivoting said support arms at right angles to the pivotal movement imparted thereto by said second gear means whereby said wheels are positively steered in the direction of the tilting thereof to facilitate the raising and lowering of the frame and the gun thereon.
 10. The mobile gun carriage of claim 9 including a plurality of equilibrator springs adjustably seated in said frame, and a follower at the end of said tow bar within said frame operatively connected with said springs for compressing said springs during the lowering of said frame into contact with the ground thereby to provide sufficient energy for raising said frame to the travel position thereof in cooperation with the external forces being applied to said tow bar.
 11. The combination defined in claim 9 including, a detent releasably engageable with said tow bar to prevent displacement thereof, means on said detent for facilitating manual disengagement thereof from said tow bar, and spring means for biasing said detent normally into engagement with said tow bar during the longitudinal displacement imparted thereto for returning the carriage to the rolling travel position thereof.
 12. The mobile gun carriage of claim 9 wherein each of said pivotal connecting means includes a pivot member, a cylindrical portion of said pivot member being rotatably seated in the side of said frame in parallelism with the longitudInal axis thereof in position to be rotated by said second gear means, a flange portion projecting outwardly from said cylindrical portion and parallel thereto to serve as a bearing surface for said support arm during the pivotal movement imparted thereto by said torsion bar means, and a rod portion extending outwardly from the center of said flange portion into rotatable engagement with said support arm to serve as an axis for the pivotal movement thereof at right angles to the direction of the pivotal movement imparted thereto by said second gear means.
 13. The mobile gun carriage of claim 9 wherein said torsion bar means comprises, a torsion bar pinned at one end thereof within said support arm adjacent said wheel, third gear means in said support arm for rotating said torsion bar in response to the pivotal movement of said support arm about an axis at right angles to the pivotal movement imparted thereto by said second gear means, and stop means for halting the rotation of said torsion bar in one direction to limit the unwinding thereof after said frame has been lowered into contact with the ground and in the opposite direction to limit the additional loading imparted thereto during the rolling travel of the carriage in the event of relative motion between said frame and said support arms.
 14. The mobile gun carriage of claim 13 wherein said means for pivotally connecting said support arms to the sides of said frame includes an outwardly projecting rod portion extending through said support arm in rotatable engagement therewith and wherein said third gear means in each of said support arms comprises, a bevel gear secured to said rod portion, and a bevel gear segment secured to the free end of said torsion bar in meshing engagement with said bevel gear whereby pivotal movement of said support arm about said rod portion actuates said gear segment to rotate said torsion bar accordingly.
 15. The mobile gun carriage of claim 14 including stop means for halting the rotation of said torsion bar comprising, a C-shaped insert fixedly secured within said support arm to straddle said bevel gear segment, and a stop surface on each end of said insert disposed in the path of movement of said bevel gear segment. 